Various techniques for detecting moving image regions from video signals have been invented.
For example, Patent Document 1 discloses that first, a current frame and a previous frame are compared by each pixel to generate inter-frame pixel information. Then, based on the inter-frame pixel information, the direction of motion and the quantity of motion of the current frame image, with respect to the previous frame image, are calculated to detect one or more motion vectors. Then, based on the motion vectors and the inter-frame pixel information, one or more moving image regions in the current frame are detected.
Meanwhile, various techniques for detecting natural image regions from video signals have been invented.
For example, Patent Document 2 discloses that first, the luminance level of all or part of the pixels, in predetermined units, of image data is detected by each frame of an input video. Then, based on the detection result, the accumulation value of the quantity of variation of the luminance level between the respective pixels, in which the luminance levels have been detected, is calculated. Then, based on the calculated accumulation value, based on an average value of the quantity of variation of the luminance level between pixels calculated by dividing the accumulation value by the number of pixels, or based on the number of pieces of edges in which the quantity of variation of the luminance level between respective pixels is within a predetermined range, it is determined whether or not an input video is a natural image.
Patent Document 3 discloses that a current frame and a previous frame of a video is compared to detect one or more updated regions, and for each of the updated regions, it is determined whether or not it is a natural image based on the color entropy.
Patent Document 1: JP 2004-341356 A
Patent Document 2: JP 2002-247611 A
Patent Document 3: JP 2005-287035 A